Spherical valve plug

ABSTRACT

The invention relates to stopcocks with spherical plugs, used in ducts for conducting fluids and it concerns more particularly the spherical plugs themselves and their method of manufacture.

United States Patent 1 lnventors Max Thevignot Chancenay;

Robert M. Schweblen, Saint-Dizier-Le- Neuf, France Jan. 28, 1969 May 4, 1971 Etablissements Thevignot Jan. 18, 1968 France Appl. No. Filed Patented Assignee Priority SPHERICAL VALVE PLUG 2 Claims, 4 Drawing Figs.

US. Cl Int. CL. Field of Search [56] I References Cited UNITED STATES PATENTS 3,246,873 4/l966 Johnson 251/315X 3,339,259 9/1967 Johnson 25l/3l5X 3,463,450 8/1969 Works 251/309 FOREIGN PATENTS 406,660 2/1934 Great Britain 251/309 Primary Examiner-M. Cary Nelson Assistant ExaminerR. B. Rothman Attorney-Otto John Munz ABSTRACT: The invention relates to stopcocks with spherical plugs, used in ducts for conducting fluids and it concerns more particularly the spherical plugs themselves and their method of manufacture.

1 Patented m .11, 1971 3,578,289

2 Sheets-Sheet 1 INVE NTOR I MAX THEVIGNOT ROBERT SCHWEBLEN ATTORNE Y N Patentea- M y .11, 1911- ..3,57s;2s9

2 Sheets-Sheet 2 INVENTORI MAX THE VIGNOT ROBERT SCHWEBLEN BY W 40:?

,ATT NEY BACKGROUND OF THE INVENTION 1. Field of the lnvention Cocks which have to support high pressure in large-sized ducts are generally domed and have a spherical plug because with this method of construction it is relatively easy to ensure that the closing is fiuidtight by means of circular sealing joints.

2. Description of the Prior Art Nevertheless, making spherical plugs presents difficulties, especially when they are large. Usually these plugs have been made of cast steel. The part which comes from the foundry passes through a special lathe which shapes its external surface. After that the worked surface is examined' very carefully to reveal faults in the metal, and these are nearly always found. For each foundry fault (grains of sand, cracks,

blowholes, etc.) it is necessary to replace metal after having made a'local cavity and then to rework the part on the lathe. Butit is still not certain that the part will be fluidtight and a test loading will often enough cause the rejection of parts on which considerable amount of utterly wasted handwork has been expended; this is translated into a serious increase in the cost price of those parts which do pass the test.

Moreover, spherical plugs in cast steel are fairly heavy particularly on account of the conditions necessary for the casting of parts which are complicated in shape.

To replace the cast steel plug, there have been proposed rotors made up starting from strip steel. A single piece of strip'by rolling, pressing anddrawing gives the external sphere of the plug and another piece of strip serves to make up the through passage; these two pieces are then assembled together by autogenous welding.

But making a steel sheet adopt the shape of a sphere is not an easy operation. for medium sizes and is impractical for very large sizes.

It has also been proposed to fashion the sphere of the plug starting from a length of tube. This is easier than starting from a sheet of steel but is still however a delicate operation. On the other hand when the sphere is formed by starting from a tube the metal is made irregular in thickness. Lastly, it is likewise impracticalfor very large sizes of plug.

In order to form a spherical plug there has also been 7 proposed the fashioning of a sheet of metal by stamping two like hemispherical rings, the placing of them opposite each other and joining along a great circle of the sphere, the making of weld seams along this great circle, the passing of a straight tubular conduit of appropriate size into the openings of the rings and the soldering of the edges of this conduit onto the interior edges of the hemispherical rings.

One thus obtains a relatively cheap plug, however, it has the following fault; when it is in a closing position in a valve the soldering of the hemispheres along a great circle is in a plane which passes through the axis of the pipe stopped up by the plug; the fluid, blocked by the plug, then exerts astrong pressure on the principal weld line of the plug, and this weld line inevitably forms an area with weak spots, no matter how much care was taken in making it. These conditions are very unsatisfactory if the cocks have to work at high pressure.

SUMMARY OFTHE INVENTION The invention has for its object spherical plugs for cocks and a process for making them in which the difficulties laid out above are avoided or diminished in their effect.

According to one aspect of the invention we provide a spherical plug including two similar hemispherical cheeks in sheet steel with their edges defined by portions of a great circle and by a half small circle with an axis perpendicular to that of the great circle, the said cheeks being assembled together by welding along their great circle so as to form a spherical surface cut into by a pair of coaxial spherical segments of which the axis is in the plane of the great circle, and a cylindrical conduit in rolled steel coaxial with the axis of the said segof the said spherical segments to form a through-passage of the plug. t

' A spherical plug, according to a general embodimentof the invention, has two substantially hemispherical cheeks in sheet steel material assembled so as to form a spherical surface cut out in the form of four spherical segments diametrically opposed two by two and forming a first pair and a second-pair, the diametrical axes of the two pairs being perpendicular, the said cheeks being welded one to the other along four weld lines on a great circle of the said spherical surface, by a cylindrical conduit in rolled steel placed along the diameter of the spherical surface which corresponds to the axis of the first pair, the said conduit being welded to the said spherical surface at the edges of the two spherical segments of the first pair and beingcontinuous between them; at the spherical segments of the second pair a bush is welded on to the said cylindrical conduit and at the other spherical segment of the second pair another bush is welded on to the said cylindrical conduit.

The process of manufacture according to the invention includes all the following steps 1 to 5i 1. cutting out in a sheet of steel two identical blanks of generally quadrangular shape of which the outline is defined by two arcs of a first pair of circles, outside each other and centered on one axis, two arcs of a second pair of circles, outside each other and centered on an axis perpendicular to that of the first pair and four straight edges joining the ends of the arcs of the circles and parallel two by two; I p

2. die-forming the said blanks so as to give to each the shape of a truncated hemisphere of an external diameter D and defined by a first pair and a second pair of half small circles, and four sectors of the same great circle corresponding to the four straight segments parallel two by two; the two hemispheres thus obtained being identical and in each pair of blanks the direction of the axes of corresponding half small circles being the same; if necessary, correcting the four great circle sectors on each of the hemispheres;

3. mounting together a steel cylindrical conduit of circular section, the interior diameter of the said conduit being d and the length of the said conduit being slightly less than the distance between the planes of the semicircles of the first pair, and the two hemispheres face-to-face and surrounding the conduit, the four great circle sectors of each hemisphere coinciding with those of the other hemisphere, the two first pairs of half small circles of each hemisphere forming a first pair of small circles, the distance between their planes being L, and their edges abutting the two ends of the conduit, the two second pairs of half small circles of each hemisphere forming a second pair of small circles, the distance between their planes being H, and giving accessto the external surface of the conduit, the common axes of the two pairs, respectively, of small circles being at right angles;

4. making in one or more operations weld lines along the four great circle sectors of the truncated sphere thus made up and along the first pair of small circles at the contact with the cylindrical conduit, so as to obtain an entity of a diameter D crossed ,by a cylindrical conduit with an internal diameter d, a height H and of which the length measured along the axis of the conduit is L; and

5. attaching by welding a bush onto the outside of the surface of the conduit and inside the sphere in each of the two cavities accessible through each of the small circles of the second pair of small circles.

The process may include the subsequent steps of:

6. reaming out the cylindrical conduit and the edges of the two small circles which are welded to it;

7. machining the external surface of the sphere.

Preferably the quantities D, d, L, H, are chosen so that the ratio D:d is about 1.50:1, the ratio Lzd is about 1.20:1, and so ments, the said cylindrical conduit being welded to the edges that the ratio Hzd is about 1.20:1.

It is however possible to construct plugs within the invention in which the three ratios mentioned are anywhere between I and 2.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood by reading the following description of one embodiment, given with reference to the attached drawings in which:

FIG. 1 represents a blank cutout of a rolled steel sheet,

FIG. 2 shows, before assembly, in perspective view the parts making up a spherical plug,

FIG. 3 shows a plug in section, the right-hand half before reaming and machining, the left-hand half after reaming and machining, and

FIG. 4 shows a finished plug.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. I there is shown a blank 1 obtained by cutting out (for example, by flame cutting) in a sheet of rolled steel to a particular shape; this shape is defined by two arcs of circles II and 12, their centers lying on an axis I6, and the two circles being outside. each other, two arcs of circle 14 and I5, their centers lying on an axis 13 perpendicular to the axis 16 and the circles being outside each other, and four straight edges 17, I7 I8, 18 joining the arcs; two opposite edges such as 17 and 17 being parallel and substantially perpendicular to the diagonal which communicates with them; in other words, the edges 17 and 17 have a common bisector.

The blank I of FIG. I is to be die-formed, e.g. by stamping and hot-forging between a die and a spherical punch to take the spherical shape; the shape of the blank is'chosen so that, after stamping: the four formerly straight edges I7, 17', I8, 18, form substantially four sectors of the same great circle of a sphere;

the two arcs l1 and 12 on the one hand, 14 and IS on the other hand, form each substantially a half small circle of the same sphere, the two first arcs forming one pair of equal half small circles parallel to each other and perpendicular to the great circle formed by the sectors I7, l7, 18, 18', the other two of these arcs forming a pair of equal half small circles parallel to each other and perpendicular at the same time to the former half small circles and to the said great circle.

In other words the shape of the blank I in FIG. I is chosen so that when it leaves the press the blank 1 takes the general shape of the hemispherical cheek shown at l in FIG. 2.

In fact what leaves the press is not exactly the check I of FIG. 2. Stamping, above all when it is spherical, gives results which are irregular and unpredictable. What is most important is the internal and external sphericity of the cheek. But the' edges of the cheek may be scalloped and have burrs.

It therefore may be necessary to subject the part leaving the press to a correction at least of the four great circle sectors, preferably with an appropriate chamfer. Because of the choice which has been made for the shape for the blank before stamping this correction will only remove a trivial quantity of metal.

It is then that the hemispherical cheek shown at l in FIG. 2 is obtained.

The straight edges 17, I7, I8, 18, of FIG. 1 have become in FIG. 2 circular sectors indicated by the same references all positioned on the same great circle 19 of a sphere shown by a dotted line. The arcs II and 12 now form two half small circles of the same sphere parallel to each other and perpendicular to the plane of the great circle 19. In the same way the arcs l4, 15, have become two half small circles of the same sphere parallel to each other and perpendicular at the same time to the half small circles ll, 12, and to the great circle 19. In other words, the axis of the great circle 19, that of the half small circles l1 and 12 and that of the half small circles 14 and I form a trirectangular trihedron.

From FIG. 2 one can also see another cheek 2 exactly like cheek I and obtained in the same way as the latter. The parts of the cheek 2 will receive the same reference numbers, plug l0, as the corresponding parts of the check 1.

In FIG. 2, there is shown a portion of circular cylindrical tube 3 likewise of steel but thicker than the checks 1 and 2. This tubular element has a length slightly less than the distance L between the planes of the half circles I1 and 12 (or 21 and 22) and its internal diameter d is slightly greater than that of these four semicircles.

In FIG. 2 there are also shown two parts 4 and 5 destined to form bushes. These are parts of full cylinders defined on one side by a straight cut such as 51 and on the other side by a cylindrical surface 52 having the same radius as the tube 3.

In order to understand more clearly how the assembly of the parts in FIG. 2 is carried out to make up the plug shown in FIG. 4 we shall refer to FIG. 3 (in section), and more particularly to the right-hand part of this FIG. FIG. 3 corresponds to a section taken through the great circle 19 when this has been brought into contact with the great circle 29, that is to say, it is a section through the vertical plane passing through the axis 31 of the tube 3', this section is seen from the right referred to in FIG. 2. The inside of the side of the tube 3 which is within the hemispherical cheek l and a small part of the interior surface of this cheek are visible.

To assemble the parts the tubular element 3 is arranged on a jig, the axis of the element being at 31 and about this element the hemispherical checks 1 and 2 are positioned; check 1 only is seen partially in FIG. 3 in its part-finished state, particularly the sectors 17 and 18 of the great circle and its half small cir-' sphere formed by the two hemispherical cheeks, the two checks are fixed onto the tubular element 3. The weld seam 32 is shown in section at I32. The cheeks l and 2 are also fastened one to the other by means of four weld seams between the sectors 17 and 27', 17 and 27, 18' and 28, and 18 and 28, respectively. These are made in one or more operations. Because of the section taken, these weld seams are not visible on FIG. 3 but are shown in FIG. 4.

Then the parts 4 and 5 of FIG. 2 are welded onto the tube 3 by welds 43 and 53 at the spherical segments defined by the small circles I4, 24; I5, 25, through the opening offered by these circles.

At this stage the assembly corresponds to the right-hand part of FIG. 3. One then proceeds to the machining of the bush parts 4 and 5. Part 4 is destined to serve as a guide journal and there is drilled into it a centering hole 44 (seen in the left-hand part of FIG. 3). Part 5 destined to act as a drive journal receives two blind threaded holes one of which is visible at 54, and a housing 55 (best seen from FIG. 4) to drive the journal in known manner. The blind threaded holes allow for the screwing in of threaded eyes for the handling of the plug.

The part thus made up has the general appearance shown in FIG. 4. It is a truncated sphere of which the diameter is D and of which the height is H (see FIGS. 2 and 3). It is crossed by a conduit of interior diameter d and having a total length L (external measurement). These four quantities are preferably linked in the three relationships indicated above.

This made-up part is commonly quite heavy. After having screwed the threaded eyes into the blind threaded holes of the part 5, which allows for the handling of the part by mechanical means, one withdraws it from the jig and one places it on a reamer in order to ream out the inside of the cylinder 3; on the left-hand side of FIG. 3 the dotted line 33 represents the measurement before reaming and the line 34 shows the measurement after reaming. In the course of this operation the weld line 35 which is similar to the line 32 is thinned; the part 118 of the check 1 goes, which causes the circular sector 18' to be cut in a bevel (as shown in FIG. 4).

This done the plug is moved on to a special lathe in order to accurately machine the external surface of the sphere; in the course of this, the measurement of the external surface of the sphere shown as a dottedline at 127 in the left hand partof FIG. 3 becomes that shown by the sector of the circle 117. The difference between the measurements before and after machining of the external surface of the plughas deliberately been exaggerated to make the drawing clearer. In fact the thickness of the shaving removed is' very small; this thickness can be considerably less than for the correction madeto a plug made in cast steel. One can therefore adopt a higher speed of cut which reduces the machining time.

In the embodiment described, a spherical plug is obtained which is lighter and more resistant than those in cast steel, and more resistant also than previous spherical plugs made from strip steel; this process is also suitable for the manufacture of large-sized plugs. One can be sure that the metal is sound because the starting material is rolled sheet steel. Practically no parts are rejected in test. On the other hand when a plug embodying the invention is in closed position in a cock, the conduit 3 is perpendicular to, the principal pipe and the great circle 19 is placed transversely. The fluid blocked by the closure of the cock exerts its pressure on whichever of the checks 1 or 2 which blocks it, and this pressure tends to press the cheek towards one another; it therefore does not make the welds work which join these cheeks together. The surface of the plug which acts is all of a piece, without weld, and it is 1 made up of rolled steel which can have been checked, before stamping. to be perfectly sound.

It is only when the plug is in the open position that the fluid is in contact with the great circle weld, but then the pressure exerted is less and the weld is not submitted to any considerable force.

We claim:

l. A spherical plug for a ball valve comprising a truncated hollow spherical housing having an inlet and an outlet arranged along a common longitudinal axis, said housing including a pair of similar hemispherical cheeks made of sheet steel of substantially constant thickness, assembled to form the spherical surface and cutout in the form of four spherical segmerits diametrically opposed two by two and forming a first pair and a second pair, the diametrical axis of the two pairs being perpendicular,

said housing in its assembled form being limited by said pairs of symmetrical circular edges, and an inner cylindrical conduit made of rolled steel coaxial with said circular edges and being disposed on said longitudinal axis within said spherical housing, said cylindrical conduit being provided with two plane ends and assembled within said spherical housing by circular weld lines wherein the circular edges of said housing overlap the plane ends of said cylindrical conduit and whereby a lightweight watertight plug is formed. 2. A spherical plug according to claim 1 wherein said circular weld lines are laid upon the inner face of said spherical housing. 

1. A spherical plug for a ball valve comprising a truncated hollow spherical housing having an inlet and an outlet arranged along a common longitudinal axis, said housing including a pair of similar hemispherical cheeks made of sheet steel of substantially constant thickness, assembled to form the spherical surface and cutout in the form of four spherical segments diametrically opposed two by two and forming a first pair and a second pair, the diametrical axis of the two pairs being perpendicular, said housing in its assembled form being limited by said pairs of symmetrical circular edges, and an inner cylindrical conduit made of rolled steel coaxial with said circular edges and being disposed on said longitudinal axis within said spherical housing, said cylindrical conduit being provided with two plane ends and assembled within said spherical housing by circular weld lines wherein tHe circular edges of said housing overlap the plane ends of said cylindrical conduit and whereby a lightweight watertight plug is formed.
 2. A spherical plug according to claim 1 wherein said circular weld lines are laid upon the inner face of said spherical housing. 